This invention relates to a process for treating an aqueous solution containing ferric and other metal ions for selectively removing the ferric ion.
When ferric ion is intended to be selectively separated from an acidic solution containing various metal ions, a neutralising agent such as calcium carbonate or calcium hydroxide is generally added to the acidic solution to selectively precipitate the ferric ion as ferric hydroxide. This method is, however, not applicable to an acidic solution having a high ferric ion concentration such as a hydrochloric acid solution of manganese nodules, because colloidal ferric hydroxide is produced in such a large amount that a solid-liquid separation is inhibited. Moreover, this method when applied to a large scale treatment, is disadvantageous from economic point of view because the neutralising agent is not available at a low cost.
Recent trend of metal refining industries is towards hydro-metallurgy in favor of its decreased energy consumption. Thus, there is a great demand to develop a simple and economical process for removing ferric ion from acidic aqueous solutions containing various metal ions, which removal is indispensable to selectively recover desired metals therefrom.